Pneumatic control system and relay valve construction therefor or the like

ABSTRACT

A relay valve construction comprising a housing means having an inlet and a pair of outlets respectively interconnected to the inlet by a pair of valve seats controlled in an alternate manner by a valve member interconnected to a diaphragm means which is normally biased to one position thereof by a spring means and is adapted to be moved to another position thereof by a first pilot valve means directing a pilot pressure signal against one side of the diaphragm means, a second pilot valve means being provided for directing a canceling pilot pressure signal against the other side of the diaphragm means to move the same back to its one position in opposition to the force of the first-named pilot signal to thereby cancel the effect thereof.

United States Patent [72] Inventor Joseph P. Wagner Knoxville, Tenn.[21] Appl. No. 835,395 [22] Filed June 23, 1969 [45] Patented Apr. 20,1971 [73] ,Assignee Robertshaw Control Company Richmond, Va.

[54] PNEUMATIC CONTROL SYSTEM AND RELAY VALVE CONSTRUCTION THEREFOR ORTHE LIKE 8 Claims, 3 Drawing Figs.

[52] U.S. Cl 137/6255, 251/31 [51] Int. Cl ..F16k 31/365 [50] Field ofSearch 137/6255, 102; 251/31 [56] References Cited UNITED STATES PATENTS251,897 1/1882 Kneeland 137/102 1,506,012 8/1924 Lewis 137/102X3,134,395 5/1964 Glasgow l37/625.5X 3,155,365 11/1964 Hartung et al.25l/31X Primary ExaminerM. Cary Nelson Assistant Examiner-Michael O.Sturm Attrney-Candor, Candor and Tassone ABSTRACT: A relay valveconstruction comprising a housing means having an inlet and a pair ofoutlets respectively interconnected to the inlet by a pair of valveseats controlled in an alternate manner by a valve member interconnectedto a diaphragm means which is normally biased to one position thereof bya spring means and is adapted to be moved to another position thereof bya first pilot valve means directing a pilot pressure signal against oneside of the diaphragm means, a second pilot valve means being providedfor directing a canceling pilot pressure signal against the other sideof the diaphragm means to move the same back to its one position inopposition to the force of the first-named pilot signal to therebycancel the effect thereof.

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sum 1 or 2 INVENTOR. JOSEPH P. WAGNER ms ATTORNEYS FIGJ PATENTEDAPRZOIHYI 3575211 sum 2 0 2 INVENTOR.

JOSEPH P. WAGNER HIS ATTORNEYS PNEUMATM CUNTROIL SYSTEM AND lltllElLAi!VAlLl/IE CONSTRUCTION THEREFOR OR THE MMIE This invention relates to animproved pneumatic control system as well as to an improved relay valveconstruction for such a control system or the like.

It is well known that various pneumatic control systems have beenprovided for engine control purposes and the like wherein many separatevalve parts are provided to function in a desired manner.

One of the features of this invention is to provide a relay valveconstruction which is adapted to transfer the flow from a main pressuresource to two different pneumatically operated devices in an alternatemanner by the use of a single valve member of the relay valveconstruction.

Another feature of this invention is to provide such a transfer from onemain valve seat of the relay valve construction to the other thereofwith a snap action so that no modulation is provided by the relay valveconstruction.

Another feature of this invention is to provide such transfer means byutilizing pilot valve means in the relay valve construction.

In particular, one embodiment of this invention provides a relay valveconstruction having a housing means provided with an inlet and a pair ofoutlets respectively interconnected to the inlet by a pair of valveseats, a movable valve member being provided for opening and closing thevalve seats in an alternate manner. A diaphragm means is carried by thehousing means and is operatively interconnected to the valve member tocontrol movement thereof, the diaphragm means cooperating with thehousing means to define a chamber therewith on one side of the diaphragmmeans. A spring means is carried by the housing means and normally tendsto move the diaphragm means to one position thereof to cause the valvemember to close one of the valve seats and open the other valve seat sothat the inlet is only and normally interconnected to the outletassociated with the other valve seat. A pilot valve means is carried bythe housing means and is adapted when in one position thereof tointerconnect the chamber with the atmosphere and when in anotherposition thereof to interconnect a pilot pressure signal to the chamberto act on the diaphragm means to move the same in opposition to thespring means and cause the valve member to close the other valve seatand open the one valve seat so that the inlet is now only interconnectedto the normally closed outlet associated with the one valve seat.Another pilot valve means is carried by the housing means and is adaptedwhen in one position thereof to interconnect another chamber on theother side of the diaphragm means with the atmosphere and when inanother position thereof to interconnect a canceling pressure signal tothe other chamber to act on the diaphragm means and cause the same tomove in opposition to the pressure signal in the first-named chamberback to its one position so that the valve member again closes the onevalve seat and opens the other valve seat whereby the inlet is againonly interconnected to the normally open outlet associated with theother valve seat.

Accordingly, it is an object of this invention to provide an improvedcontrol system having one or more of the novel features of thisinvention as set forth above or hereinafter shown or described.

Another object of this invention is to provide an improved relay valveconstruction having one or more of the novel features set forth above orhereinafter shown or described.

Other objects, uses and advantages of this invention are apparent from areading of this description which proceeds with reference to theaccompanying drawings forming a part thereof and wherein:

FIG. I is a cross-sectional view of the relay valve construction of thisinvention with the relay valve construction illustrated in one of itsoperating positions and being utilized in the control system of thisinvention which is schematically illustrated.

FIG. 2 is a view similar to FIG. 1, except in reduced form, andillustrates the relay valve construction in another operating positionthereof.

FIG. 3 is a view similar to FIG. 2 and illustrates the relay valveconstruction in another operating position thereof.

While the various features of this invention are hereinafter describedand illustrated as being particularly adapted to provide the relay valveconstruction for a particular pneumatic control system of thisinvention, it is to be understood that the various features of thisinvention can be utilized singly or in any combination thereof toprovide relay valve means for other systems as desired.

Therefore, this invention is not to be limited to only the embodimentillustrated in the drawings, because the drawings are merely utilized toillustrate one of the wide variety of uses of this invention.

Referring now to FIG. l, the improved control system of this inventionis generally indicated by the reference numeral It) and comprises a mainpneumatic pressure source 11, a pair of pneumatically operated devices12 and 1 .3, a pneumatic pilot pressure signal source 14, a cancelingpneumatic pilot pressure signal source t5, and a relay valveconstruction 16 of this invention operatively interconnected to themeans lll5 in a manner hereinafter described to provide means fortransferring the pneumatic source ll in an alternate manner to thepneumatically operated devices 12 and 13 in a simple and effectivemanner without modulation of the flow of pressure fluid between thedevices 12 and 13 as will be apparent hereinafter.

The relay valve construction 16 comprises a housing means l7 formed froma plurality of housing parts KS, 19, 20, 21, 22 and 23 suitably fastenedand sealed together in the stacked relation illustrated in FIG. l andcarrying bracket means 24 and 25 at the opposed ends thereof foreffectively mounting the relay valve construction 16 to any desiredsupporting structure.

The housing parts lib-23 of the housing means 17 are formed in anysuitable manner to cooperate together and define an inlet means 26adapted to be interconnected to a conduit means 27 leading from the mainpressure source 11, the inlet means as also being adapted to beinterconnected by a pair of axially aligned and axially spaced valveseats 28 and 29 to outlet means Iltl and 31 formed in the housing means17 and being respectively interconnected to the pneumatically operateddevices 112 and 13 by suitable conduit means 32 and 33.

However, a poppet valve member 34 is disposed in the housing means 17between the valve seats 28 and 29 to control the same in an alternatemanner so that when the valve member 1% closes against the upper valveseat 29, as illustrated in FIG. i, the inlet means as is onlyinterconnected to the outlet means 30. When the valve member M is movedagainst the valve seat 28 as illustrated in FIG. 2, the inlet 26 is onlyinterconnected to the outlet 31.

The valve member 34 is interconnected to a valve stem means N which isaxially movable in an opening 36 passing through the housing part 211and is interconnected to a diaphragm backup member or shoe 37, theopening 36 being sealed by an O-ring 3b and washerlike member 39telescopically disposed about the valve stem 35. A main flexiblediaphragm ll) cooperates with the housing parts 19 and 20 to definechambers dll and 42 on opposite sides of the diaphragm d ll with suchchambers dll and 42 being sealed from each other by the diaphragm member40. The diaphragm it} can be interconnected to the diaphragm backupplate or shoe 3'7 in any suitable manner so that the valve stem35 and,thus, the valve member 34 will follow movement of the diaphragm at) aswill be apparent hereinafter.

A compression spring 43 is disposed in the chamber 42 and has one end Mbearing against the diaphragm backup member or shoe 37' while the otherend 4l thereof bears against the washer 39 so that the force of thecompression spring 43 always tends to maintain the diaphragm member 49in the up position as illustrated in FIG. 1 to thereby hold the valvemember 34 in seating engagement against the valve seat 29 so as toprevent fluid communication between the inlet 26 and outlet 31 whilenormally permitting fluid communication between the inlet 26 and theoutlet 30.

Two pilot valve means, generally indicated by the reference numerals 46and 47, are respectively carried by the housing means 17 at the opposedends thereof. The pilot valve means 46 and 47 comprising stationaryvalve seats 48 respectively leading to the chambers 41 and 42 in amanner hereinafter described and flexible diaphragms 49 carried by thehousing means 17 and normally being urged to their closed positionsagainst their respective valve seats 48 by compression springs 50whereby when the diaphragm 49 of the pilot valve means 46 is in itsclosed position against its respective valve seat 48, a pilot pressuresignal inlet means 51 formed in the housing part 19 is prevented fromcommunicating with the chamber 41 through the valve seat 48 andinterconnecting passage means 52. Similarly, the diaphragm 49 of thepilot valve means 47 is disposed in its closed position against itsrespective valve seat 48, a pilot pressure signal inlet means 53 formedin the housing part 22 is prevented from communicating with the chamber42 through the valve seat 48 and its interconnecting passage means 54formed through the housing parts 22 and 21 as illustrated in FIG. 1.

The pilot signal inlet means 51 is interconnected to the pilot pressuresignal source 14 by suitable conduit means 55 while the pilot signalinlet means 53 is interconnected to the canceling pilot pressure signalsystem 15 by suitable conduit means 56.

Each diaphragm 49 of the pilot valve means 46 and 47 has an opening 57passing therethrough in aligned relation with its respective valve seat48 and in aligned relation with a movable valve seat 58 that moves inunison with the respective diaphragm 49. The housing parts 18 and 23respectively carry stationary valve members 59 disposed spaced fromtheir respective movable valve seats 58 so as to permit fluidcommunication between atmosphere or vent ports 60 thereof, through therespective open valve seats 58, and the respective chambers 41 and 42when the diaphragms 49 are in their closed positions against theirrespective valve seats 48.

1n this manner, as long as the diaphragms 49 are closing the respectivevalve seats 48, as illustrated in FIG. 1, the chambers 41 and 42 of thehousing means 17 are at atmospheric condition so that the compressionspring 43 maintains the flexible diaphragm 40 in its up position tomaintain the valve member 34 closed against the valve seat 29 wherebythe outlet means 30 is normally open and the outlet means 31 is normallyclosed.

From the above description, it can be seen that the pneumatic controlsystem and pneumatic relay valve construction 16 of this invention canbe formed of relatively few parts in a simple and economical manner tobe operated in a manner now to be described.

With the signal sources 14 and being in the 08 condition as illustratedin F10. l and with the main pneumatic source 11 being in the oncondition as illustrated in H0. 1, it can be seen that the compressionspring 43 maintains the diaphragm 40 in its up position so that thevalve member 34 is closing the valve seat 29 while maintaining the valveseat 28 in an open condition whereby the pneumatic source 11 is only andnormally interconnected by the relay valve construction 16 of thisinvention to the pneumatically operated device 12 through the openedvalve seat 28.

However, when the operator or suitable automatic means causes thepneumatic signal source 14 to be directed through the conduit means 55to the relay construction 16 as illustrated in FIG. 2, the force of thepneumatic fluid being directed through the inlet means 51 against theunder side of the diaphragm 49 of the pilot valve means 46 builds up inthe inlet means 51 under the diaphragm 49 outside of the periphery ofthe valve seat 48 until the opposing load exerted by the compressionspring 50 is overcome. At this time. the

diaphragm 49 moves slightly away from the valve seat 48 and the signalpressure is applied to the full area of the under side of the diaphragm49 so that the same will snap to its uppermost position with the valveseat 58 thereof closed against the stationary valve member 59 asillustrated in FIG. 2 so as to prevent loss of signal pressure outthrough the valve seat 58 and its associated atmosphere port 60.

The pneumatic signal fluid in the inlet means 51 is now free to flowthrough the opened valve seat 48 of the pilot valve means 46 in themanner illustrated in FIG. 2 and into the chamber 41 to act against theupper side of the diaphragm 40 in opposition to the force of thecompression spring 43. With the chamber 41 now being almost immediatelypressurized upon the snap opening of the valve seat 48 of the pilotvalve means 46, the resulting pressure difierential now acting acrossthe diaphragm 40 causes the diaphragm 40 and, thus, the valve stem means35 and valve member 34 to move downwardly from the position of FIG. 1 tothe position of FIG. 2 with substantially a snap action to close thevalve seat 28 and open the valve seat 29 whereby the pneumatic pressuresource 11 is disconnected from the pneumatically operated device 12 andis only interconnected to the pneumatically operated device 13 throughthe normally closed, but now opened valve seat 29. This snap movement ofthe main valve member 34 prevents any modulated flow of pressure fluidto the device 13.

Thus, the relay valve construction 16 remains in the positionillustrated in H0. 2 as long as the pneumatic signal source 14 is beingdirected to the inlet means 51 of the relay valve construction 16.However, if it is desired to switch the pneumatic pressure source 11back to the pneumatically operated device 12 while the pneumatic signalsource 14 is still being interconnected to the inlet means 51 of thehousing means 16, the canceling pneumatic signal source 15 is eitherinterconnected manually or automatically to the inlet means 53 in themanner illustrated in FIG. 3 whereby the buildup of signal pressure inthe inlet means 53 is applied against the upper side of the diaphragm 49of the pilot valve means 47 outside the periphery of the valve seat 48thereof to overcome the force of the compression spring 50 and snap thediaphragm 49 downwardly as illustrated in FIG. 3, in the same mannerpreviously described for the pilot valve means 46, to close the valveseat 58 and open the valve seat 48 so that pressure fluid is now appliedthrough the passage means 54 to the chamber 42.

The pressure fluid now being directed into the chamber 42 of the relayvalve construction 16 cancels the effect of the existing pressure on thetop side of the diaphragm 40 whereby the compression spring 43 forcesthe diaphragm 40 and, thus, the valve stem 35 and valve member 34upwardly with substantially a snap action to again seat the valve member34 against the valve seat 29 in the manner illustrated in FIG. 3 so thatthe main pressure source 11 is disconnected from the pneumaticallyoperated device 13 and is transferred back to the pneumatically operateddevice 12 without any modulated flow of pressure fluid to the device 12whereby the relay construction 16 will remain in the conditionillustrated in FIG. 3 as long as the pneumatic signal sources 14 and 15are being respectively directed to the inlet means 51 and 53 of thehousing means 17.

With the relay valve construction 16 now disposed in the conditionillustrated in FIG. 3, a subsequent disconnection of the cancelingpressure source 15 from the inlet means 53 causes the compression spring50 of the pilot valve means 47 to return the diaphragm 49 against thevalve seat 48 so that the movable valve member 58 thereof is now openedto vent the pressure in chamber 42 to the atmosphere through the ventport 60 of the housing part 23 whereby the pressure fluid in chamber 41again forces the valve member 34 downwardly against the valve seat 28 toswitch the pressure source 11 from the pneumatically operated device 12back to the pneumatically operated device 13 as illustrated in FIG. 2.

I engaging With the relay valve construction l6 now disposed in theposition illustrated in H0. 2, a subsequent disconnection of thepneumatic signal source 14 from the inlet means 51 will cause thecompression spring 50 of the pilot valve means 46 to move the diaphragm49 thereof downwardly to close the valve seat 53 and open the valve seat53 as illustrated in H6. 1 so that the chamber ll is now vented to theatmosphere through the vent port 60 of the housing part 1% whereby thecompression spring 43 will move the diaphragm 40 and, thus, the valvestem means 35 and valve member 34 upwardly to close the valve seat 29and open the valve seat 28 to thereby switch the pneumatic pressuresource ill from the pneumatically operated device 13 back to thepneumatically operated device 12 as illustrated in FIG. 1.

Therefore, it can be seen that in the control system ill) of thisinvention, the relay valve construction 16, when supplied only with thepneumatic source ill, will direct such source fluid out through thenormally opened outlet means 30 to the device 12. With pilot inlet meansSll being pressurized, the relay valve construction l6 transfers with asnap action so that the source fluid is now directed out of the normallyclosed outlet means 311 to the device 13. The effect of subsequentlysupplying pressure fluid to the inlet means 53 of the relay valveconstruction 16 cancels the effect of the signal pressure at the inletmeans 51 thereof and thereby returns the valve member 3% to its normalposition with a snap action so that the source fluid flows out of thenormally opened outlet means 30.

Accordingly, it can be seen that this invention not only provides animproved pneumatic control system, but also this invention provides animproved pneumatic relay valve construction for such a control system ofthe like.

lclaim:

l. A relay valve construction comprising a housing means having an inletand a pair of outlets respectively interconnected to said inlet by apair of valve seats, a movable valve member for opening and closing saidvalve seats in an alternate manner, a diaphragm means carried by saidhousing means and being operatively interconnected to said valve member,said diaphragm means cooperating with said housing means to define achamber therewith on one side of said diaphragm means, spring meanscarried by said housing means and normally tending to move saiddiaphragm means to one position thereof to cause said valve member toclose one of said valve seats and open the other valve seat so that saidinlet is only interconnected to the outlet associated with said othervalve seat, and pilot valve means carried by said housing means andbeing adapted when in one position thereof to interconnect said chamberwith the atmosphere and when in another position thereof to interconnecta pilot pressure signal to said chamber to act on said diaphragm meansto move in opposition to said spring means and cause said valve memberto close said other valve seat and open said one valve seat so that saidinlet is only interconnected to the outlet associated with said onevalve seat, said pilot valve means comprising a flexible diaphragmcarried by said housing means, said pilot valve means further comprisinga valve seat means carried by said housing means and being adapted tointerconnect said pilot signal to said chamber, said pilot valvediaphragm when said valve seat means preventing fluid communicationbetween said pilot signal and said chamber, said pilot valve diaphragmhaving an opening therethrough aligned with said valve seat means, saidopening being adapted to interconnect the atmosphere to said chamberthrough said valve seat means when said pilot diaphragm seats againstsaid valve seat means.

2. A relay valve construction as set forth in claim ll wherein saidopening through said pilot valve diaphragm defines a movable valve seatthat is in an open condition when said pilot diaphragm seats againstsaid valve seat means, said housing means having a stationary valvemember which is engaged by said movable valve seat when said pilot valvediaphragm moves away from said valve seat means to interconnect saidpilot signal to said chamber whereby said stationary valve member closessaid movable valve seat to prevent fluid communication between saidchamber and the atmosphere.

3. A relay valve construction comprising a housing means having an inletand a pair of outlets respectively interconnected to said inlet by apair of valve seats, a movable valve member for opening and closing saidvalve seats in an alternate manner, a diaphragm means carried by saidhousing means and being operatively interconnected to said valve member,said diaphragm means cooperating with said housing means to define achamber therewith on one side of said diaphragm means, spring meanscarried by said housing means and normally tending to move saiddiaphragm means to one position thereof to cause said valve member toclose one of said valve seats and open the other valve seat so that saidinlet is only interconnected to the outlet associated with said othervalve seat, pilot valve means carried by said housing means and beingadapted when in one position thereof to interconnect said chamber withthe atmosphere and when in another position thereof to interconnect apilot pressure signal to said chamber to act on said diaphragm means tomove in opposition to said spring means and cause said valve member toclose said other valve seat and open said one valve seat so that saidinlet is only interconnected to the outlet associated with said onevalve seat, the other side of said diaphragm means cooperating with saidhousing means to define another chamber therewith, and another pilotvalve means being carried by said housing means and being adapted whenin one position thereof to interconnect said other chamber with theatmosphere and when in another position thereof to interconnect acanceling pressure signal to said other chamber to act on said diaphragmmeans and cause the same to move in opposition to the pressure signal insaid first-named chamber back to its said one position so that saidvalve member again closes said one valve seat and opens said other valveseat whereby said inlet is again only interconnected to the outletassociated with said other valve seat, each said pilot valve meanscomprising a flexible diaphragm carried by said housing means, each saidpilot valve means further comprising a valve seat means carried by saidhousing means and being adapted to interconnect its respective signal toits respective chamber, each said pilot valve diaphragm when engagingits respective valve seat means preventing fluid communication betweenits respective signal and its respective chamber, each said pilot valvediaphragm having an opening therethrough aligned with its respectivevalve seat means, each said opening being adapted to interconnect theatmosphere to its respective chamber through its respective valve seatmeans when its respective pilot diaphragm seats against its respectivevalve seat means.

4. A relay valve construction as set forth in claim 3 wherein each saidopening through its respective pilot valve diaphragm defines a movablevalve seat that is in an open condition when its respective pilotdiaphragm seats against its respective valve seat means, said housingmeans having a pair of stationary valve members which are respectivelyengaged by said movable valve seats when said pilot valve diaphragmsmove away from their respective valve seat means to interconnect theirrespective signals to their respective chambers whereby said stationaryvalve members respectively close said movable valve seats to preventfluid communication between said chambers and the atmosphere.

5. A control system comprising a pair of pneumatically operated devices,a main pneumatic source, a pilot pressure signal source, a housing meanshaving an inlet and a pair of outlets respectively interconnected tosaid inlet by a pair of valve seats, means interconnecting said inletwith said main pressure source and interconnecting said pneumaticallyoperated devices respectively with said outlets, a movable valve memberfor opening and closing said valve seats in an alternate manner, adiaphragm means carried by said housing means and being operativelyinterconnected to said valve member, said diaphragm means cooperatingwith said housing means to define a chamber therewith on one side ofsaid diaphragm means, spring means carried by said housing means andnormally tending to move said diaphragm means to one position thereof tocause said valve member to close one of said valve seats and open theother valve seat so that said inlet is only interconnected to the outletassociated with said other valve seat, and pilot valve means carried bysaid housing means and being adapted when in one position thereof tointerconnect said chamber with the atmosphere and when in anotherposition thereof to interconnect said pilot pressure signal source tosaid chamber to act on said diaphragm means to move in opposition tosaid spring means and cause said valve member to close said other valveseat and open said one valve seat so that said inlet is onlyinterconnected to the outlet associated with said one valve seat, saidpilot valve means comprising a flexible diaphragm carried by saidhousing means, said pilot valve means further comprising a valve seatmeans carried by said housing means and being adapted to interconnectsaid pilot signal source to said chamber, said pilot valve diaphragmwhen engaging said valve seat means preventing fluid communicationbetween said pilot signal source and said chamber, said pilot valvediaphragm having an opening thercthrough aligned with said valve seatmeans, said opening being adapted to interconnect the atmosphere to saidchamber through said valve seat means when said pilot diaphragm seatsagainst said valve seat means.

6. A control system as set forth in claim wherein said opening throughsaid pilot valve diaphragm defines a movable valve seat that is in anopen condition when said pilot diaphragm seats against said valve seatmeans, said housing means having a stationary valve member which isengaged by said movable valve seat when said pilot valve diaphragm movesaway from said valve seat means to interconnect said pilot signal sourceto said chamber whereby said stationary valve member closes said movablevalve seat to prevent fluid communication between said chamber and theatmosphere.

7. A control system comprising a pair of pneumatically operated devices,a main pneumatic source, a pilot pressure signal source, a housing meanshaving an inlet and a pair of outlets respectively interconnected tosaid inlet by a pair of valve seats, means interconnecting said inletwith said main pressure source and interconnecting said pneumaticallyoperated devices respectively with said outlets, a movable valve memberfor opening and closing said valve seats in an alternate manner, adiaphragm means carried by said housing means and being operativelyinterconnected to said valve member, said diaphragm means cooperatingwith said housing means to define a chamber therewith on one side ofsaid diaphragm means, spring means carried by said housing means andnormally tending to move said diaphragm means to one position thereof tocause said valve member to close one of said valve seats and open theother valve seat so that said inlet is only interconnected to the outletassociated with said other valve seat, pilot valve means carried by saidhousing means and being adapted when in one position thereof tointerconnect said chamber with the atmosphere and when in anotherposition thereof to interconnect said pilot pressure signal source tosaid chamber to act on said diaphragm means to move in opposition tosaid spring means and cause said valve member to close said other valveseat and open said one valve seat so that said inlet is onlyinterconnected to the outlet associated with said one valve seat, theother side of said diaphragm means cooperating with said housing meansto define another chamber therewith, a canceling pilot pressure signalsource, and another pilot valve means being carried by said housingmeans and being adapted when in one position thereof to interconnectsaid other chamber with the atmosphere and when in another positionthereof to interconnect said canceling pressure signal source to saidother chamber to act on said diaphragm means and cause the same to movein opposition to the pressure signal in said firstnamed chamber back toits said one position so that said valve member again closes said onevalve seat and opens said other valve seat whereby said inlet is againonly interconnected to the outlet associated with said other valve seat,each said pilot valve means comprising a flexible diaphragm carried bysaid housing means, each said pilot valve means further comprising avalve seat means carried by said housing means and being adapted tointerconnect its respective signal source to its respective chamber,each said pilot valve diaphragm when engaging its respective valve seatmeans preventing fluid communication between its respective signalsource and its respective chamber, each said pilot valve diaphragmhaving an opening thercthrough aligned with its respective valve seatmeans, each said opening being adapted to interconnect the atmosphere toits respective chamber through its respective valve seat means when itsrespective pilot diaphragm seats against its respective valve seatmeans.

8. A control system as set forth in claim 7 wherein each said openingthrough its respective pilot valve diaphragm defines a movable valveseat that is in an open condition when its respective pilot diaphragmseats against its respective valve seat means, said housing means havinga pair of stationary valve members which are respectively engaged bysaid movable valve seats when said pilot valve diaphragms move away fromtheir respective valve seat means to interconnect their respectivesignal sources to their respective chambers whereby said stationaryvalve members respectively close said movable valve seats to preventfluid communication between said chambers and the atmosphere.

1. A relay valve construction comprising a housing means having an inletand a pair of outlets respectively interconnected to said inlet by apair of valve seats, a movable valve member for opening and closing saidvalve seats in an alternate manner, a diaphragm means carried by saidhousing means and being operatively interconnected to said valve member,said diaphragm means cooperating with said housing means to define achamber therewith on one side of said diaphragm means, spring meanscarried by said housing means and normally tending to move saiddiaphragm means to one positioN thereof to cause said valve member toclose one of said valve seats and open the other valve seat so that saidinlet is only interconnected to the outlet associated with said othervalve seat, and pilot valve means carried by said housing means andbeing adapted when in one position thereof to interconnect said chamberwith the atmosphere and when in another position thereof to interconnecta pilot pressure signal to said chamber to act on said diaphragm meansto move in opposition to said spring means and cause said valve memberto close said other valve seat and open said one valve seat so that saidinlet is only interconnected to the outlet associated with said onevalve seat, said pilot valve means comprising a flexible diaphragmcarried by said housing means, said pilot valve means further comprisinga valve seat means carried by said housing means and being adapted tointerconnect said pilot signal to said chamber, said pilot valvediaphragm when engaging said valve seat means preventing fluidcommunication between said pilot signal and said chamber, said pilotvalve diaphragm having an opening therethrough aligned with said valveseat means, said opening being adapted to interconnect the atmosphere tosaid chamber through said valve seat means when said pilot diaphragmseats against said valve seat means.
 2. A relay valve construction asset forth in claim 1 wherein said opening through said pilot valvediaphragm defines a movable valve seat that is in an open condition whensaid pilot diaphragm seats against said valve seat means, said housingmeans having a stationary valve member which is engaged by said movablevalve seat when said pilot valve diaphragm moves away from said valveseat means to interconnect said pilot signal to said chamber wherebysaid stationary valve member closes said movable valve seat to preventfluid communication between said chamber and the atmosphere.
 3. A relayvalve construction comprising a housing means having an inlet and a pairof outlets respectively interconnected to said inlet by a pair of valveseats, a movable valve member for opening and closing said valve seatsin an alternate manner, a diaphragm means carried by said housing meansand being operatively interconnected to said valve member, saiddiaphragm means cooperating with said housing means to define a chambertherewith on one side of said diaphragm means, spring means carried bysaid housing means and normally tending to move said diaphragm means toone position thereof to cause said valve member to close one of saidvalve seats and open the other valve seat so that said inlet is onlyinterconnected to the outlet associated with said other valve seat,pilot valve means carried by said housing means and being adapted whenin one position thereof to interconnect said chamber with the atmosphereand when in another position thereof to interconnect a pilot pressuresignal to said chamber to act on said diaphragm means to move inopposition to said spring means and cause said valve member to closesaid other valve seat and open said one valve seat so that said inlet isonly interconnected to the outlet associated with said one valve seat,the other side of said diaphragm means cooperating with said housingmeans to define another chamber therewith, and another pilot valve meansbeing carried by said housing means and being adapted when in oneposition thereof to interconnect said other chamber with the atmosphereand when in another position thereof to interconnect a cancelingpressure signal to said other chamber to act on said diaphragm means andcause the same to move in opposition to the pressure signal in saidfirst-named chamber back to its said one position so that said valvemember again closes said one valve seat and opens said other valve seatwhereby said inlet is again only interconnected to the outlet associatedwith said other valve seat, each said pilot valve means comprising aflexible diaphragm carried by said housing means, each said pilot vaLvemeans further comprising a valve seat means carried by said housingmeans and being adapted to interconnect its respective signal to itsrespective chamber, each said pilot valve diaphragm when engaging itsrespective valve seat means preventing fluid communication between itsrespective signal and its respective chamber, each said pilot valvediaphragm having an opening therethrough aligned with its respectivevalve seat means, each said opening being adapted to interconnect theatmosphere to its respective chamber through its respective valve seatmeans when its respective pilot diaphragm seats against its respectivevalve seat means.
 4. A relay valve construction as set forth in claim 3wherein each said opening through its respective pilot valve diaphragmdefines a movable valve seat that is in an open condition when itsrespective pilot diaphragm seats against its respective valve seatmeans, said housing means having a pair of stationary valve memberswhich are respectively engaged by said movable valve seats when saidpilot valve diaphragms move away from their respective valve seat meansto interconnect their respective signals to their respective chamberswhereby said stationary valve members respectively close said movablevalve seats to prevent fluid communication between said chambers and theatmosphere.
 5. A control system comprising a pair of pneumaticallyoperated devices, a main pneumatic source, a pilot pressure signalsource, a housing means having an inlet and a pair of outletsrespectively interconnected to said inlet by a pair of valve seats,means interconnecting said inlet with said main pressure source andinterconnecting said pneumatically operated devices respectively withsaid outlets, a movable valve member for opening and closing said valveseats in an alternate manner, a diaphragm means carried by said housingmeans and being operatively interconnected to said valve member, saiddiaphragm means cooperating with said housing means to define a chambertherewith on one side of said diaphragm means, spring means carried bysaid housing means and normally tending to move said diaphragm means toone position thereof to cause said valve member to close one of saidvalve seats and open the other valve seat so that said inlet is onlyinterconnected to the outlet associated with said other valve seat, andpilot valve means carried by said housing means and being adapted whenin one position thereof to interconnect said chamber with the atmosphereand when in another position thereof to interconnect said pilot pressuresignal source to said chamber to act on said diaphragm means to move inopposition to said spring means and cause said valve member to closesaid other valve seat and open said one valve seat so that said inlet isonly interconnected to the outlet associated with said one valve seat,said pilot valve means comprising a flexible diaphragm carried by saidhousing means, said pilot valve means further comprising a valve seatmeans carried by said housing means and being adapted to interconnectsaid pilot signal source to said chamber, said pilot valve diaphragmwhen engaging said valve seat means preventing fluid communicationbetween said pilot signal source and said chamber, said pilot valvediaphragm having an opening therethrough aligned with said valve seatmeans, said opening being adapted to interconnect the atmosphere to saidchamber through said valve seat means when said pilot diaphragm seatsagainst said valve seat means.
 6. A control system as set forth in claim5 wherein said opening through said pilot valve diaphragm defines amovable valve seat that is in an open condition when said pilotdiaphragm seats against said valve seat means, said housing means havinga stationary valve member which is engaged by said movable valve seatwhen said pilot valve diaphragm moves away from said valve seat means tointerconnect said pilot signal source to said chamber whereby saidstationary valve member closes said movable valve seat to prevent fluidcommunication between said chamber and the atmosphere.
 7. A controlsystem comprising a pair of pneumatically operated devices, a mainpneumatic source, a pilot pressure signal source, a housing means havingan inlet and a pair of outlets respectively interconnected to said inletby a pair of valve seats, means interconnecting said inlet with saidmain pressure source and interconnecting said pneumatically operateddevices respectively with said outlets, a movable valve member foropening and closing said valve seats in an alternate manner, a diaphragmmeans carried by said housing means and being operatively interconnectedto said valve member, said diaphragm means cooperating with said housingmeans to define a chamber therewith on one side of said diaphragm means,spring means carried by said housing means and normally tending to movesaid diaphragm means to one position thereof to cause said valve memberto close one of said valve seats and open the other valve seat so thatsaid inlet is only interconnected to the outlet associated with saidother valve seat, pilot valve means carried by said housing means andbeing adapted when in one position thereof to interconnect said chamberwith the atmosphere and when in another position thereof to interconnectsaid pilot pressure signal source to said chamber to act on saiddiaphragm means to move in opposition to said spring means and causesaid valve member to close said other valve seat and open said one valveseat so that said inlet is only interconnected to the outlet associatedwith said one valve seat, the other side of said diaphragm meanscooperating with said housing means to define another chamber therewith,a canceling pilot pressure signal source, and another pilot valve meansbeing carried by said housing means and being adapted when in oneposition thereof to interconnect said other chamber with the atmosphereand when in another position thereof to interconnect said cancelingpressure signal source to said other chamber to act on said diaphragmmeans and cause the same to move in opposition to the pressure signal insaid first-named chamber back to its said one position so that saidvalve member again closes said one valve seat and opens said other valveseat whereby said inlet is again only interconnected to the outletassociated with said other valve seat, each said pilot valve meanscomprising a flexible diaphragm carried by said housing means, each saidpilot valve means further comprising a valve seat means carried by saidhousing means and being adapted to interconnect its respective signalsource to its respective chamber, each said pilot valve diaphragm whenengaging its respective valve seat means preventing fluid communicationbetween its respective signal source and its respective chamber, eachsaid pilot valve diaphragm having an opening therethrough aligned withits respective valve seat means, each said opening being adapted tointerconnect the atmosphere to its respective chamber through itsrespective valve seat means when its respective pilot diaphragm seatsagainst its respective valve seat means.
 8. A control system as setforth in claim 7 wherein each said opening through its respective pilotvalve diaphragm defines a movable valve seat that is in an opencondition when its respective pilot diaphragm seats against itsrespective valve seat means, said housing means having a pair ofstationary valve members which are respectively engaged by said movablevalve seats when said pilot valve diaphragms move away from theirrespective valve seat means to interconnect their respective signalsources to their respective chambers whereby said stationary valvemembers respectively close said movable valve seats to prevent fluidcommunication between said chambers and the atmosphere.